Hey there!
There is a very good chance that the "+" is the culprit. It was probably updated with the newest update so that certain symbols couldn't be used as they would show up as weird and people would manipulate that to get very messed up usernames. I'd recommend going ahead and updating your username if you're okay with doing that. You could always just remove the "+" to see if that fixes it for you!
If you go to the Home page of FH and hit User Panel, it will ask you to sign in on the website. Once you do that, if you scroll down, you can see the option to change your username. Just type it in there, hit change, and you're good!
Glad to help! Hope to see you in the game too!